The concept of applying a heating element in a panel has been known for many, many years. A variety of different panels have been proposed and a variety of different techniques for incorporating the radiant heating elements into the panels have been used.
One of the more common systems utilizes a gypsum board into which grooves are cut and the radiant heating wires are embedded in the grooves to define a radiant heating panel. One such panel is shown in U.S. Pat. No. 3,751,630 issued Aug. 7 1973 to Brasky.
In another system a plastic laminate incorporating a film type radiant heating element has been secured either to the face of a panel or between a pair of adjacent panels. The encased element functions not only as a heating element but also defines a vapour barrier see for example U.S. Pat. No. 4,203,198 issued May 20 1980 to Hacket.
The effectiveness of the insulating overlying a radiant heating panel which is normally applied on the ceiling of a building is reduced significantly if the temperature on the side of the insulation adjacent the ceiling (the radiant heating panel) is high as the thermal efficiency of, for example, fiberglass is significantly dependent on the temperature gradiant there across.